An Epidemiological Approach to Studying Laminitis

One reason laminitis is so challenging to study is that it can result from many different primary diseases—from metabolic disorders to black walnut exposure. Researchers might be able to make headway, however, if they take an epidemiological approach to studying the disease. Epidemiologist Noah Cohen, VMD, MPH, PhD, Dipl. ACVIM, a professor in Texas A&M University's Department of Large Animal Clinical Sciences, shared how this approach might improve our understanding of laminitis at the International Equine Conference on Laminitis and Diseases of the Foot, held Nov. 1-3 in West Palm Beach, Fla.

Most laminitis researchers base their work on experimentally induced disease models (e.g., by exposing a horse to black walnut extract), which Cohen said does not accurately reflect spontaneous disease and its diverse causes. Epidemiology, on the other hand, entails studying naturally occurring disease (e.g., in a retrospective or clinical case study), with natural (“real world”) exposures that lead to disease.

"Epidemiological studies have much to offer for improving our understanding of laminitis, including identifying predisposing factors," he said. These studies are not, however, without flaw, so Cohen described both advantages and limitations to this approach.

Advantages to epidemiological studies include:

  1. Welfare In epidemiology, researchers do not create or induce disease; rather, they study naturally occurring conditions. This minimizes unnecessary animal suffering.
  2. Relevance Because epidemiological studies follow natural disease, results apply directly to natural disease (whereas experimental models do not).
  3. Multifactorial Epidemiological methods allow researchers to look at the simultaneous impact of several factors. This is important when evaluating multifactorial, complex diseases such as laminitis.
  4. Identifies risk factors By identifying risk factors that can be altered, researchers can develop methods of prevention.

Limitations Cohen mentioned include:

  1. Using real-world cases Although also an advantage, basing studies on naturally occurring disease opens the door to potential confounders beyond researchers' control (e.g., the many things that can vary among horses, such as diet, management practices, and other unrecognized factors), Cohen explained. "There is a lot of 'noise' from extraneous factors that can be difficult to filter out,” he said.
  2. Data quality How researchers gather information can influence study results. "For example, it is likely that there will be greater misclassification of laminitis when the disease is reported by owners than when the disease is reported by veterinarians," Cohen said.
  3. Hypothesis-generating Many epidemiological studies are exploratory in nature, intended to generate hypotheses rather than test them. Thus, researchers are at risk of interpreting results without recognizing the need for further substantiating findings, Cohen said.
  4. Confounding bias Researchers must be careful not to draw associations between disease and a cause related to an outside factor. "This can make an association that isn't present appear and vice versa," Cohen said. For example, say one study's results show that more Thoroughbreds colic than other breeds. It might not be the Thoroughbred breed that's associated with colic incidence, but their activity level or diet—the confounding factor.

In conclusion, Cohen said studying disease in a real-world setting has both strengths and limitations. "It's a double-edged sword," he said. To counter the limitations, he suggested having adequate expertise, time, and funding to complete these studies.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.